1 files changed, 34 insertions, 0 deletions
diff --git a/cns-libs/cnslibs/common/waiter.py b/cns-libs/cnslibs/common/waiter.py
new file mode 100644
index 00000000..89a264df
--- /dev/null
+++ b/cns-libs/cnslibs/common/waiter.py
@@ -0,0 +1,34 @@
+"""Helper object to encapsulate waiting for timeouts.
+
+Provide a Waiter class which encapsulates the operation
+of doing an action in a loop until a timeout values elapses.
+It aims to avoid having to write boilerplate code comparing times.
+"""
+
+import time
+
+class Waiter(object):
+    """A wait-retry loop as iterable.
+    This object abstracts away the wait logic allowing functions
+    to write the retry logic in a for-loop.
+    """
+    def __init__(self, timeout=60, interval=1):
+        self.timeout = timeout
+        self.interval = interval
+        self.expired = False
+        self._attempt = 0
+        self._start = None
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        if self._start is None:
+            self._start = time.time()
+        if time.time() - self._start > self.timeout:
+            self.expired = True
+            raise StopIteration()
+        if self._attempt != 0:
+            time.sleep(self.interval)
+        self._attempt += 1
+        return self